The purpose of this quality assurance project in the University Hospitals in Leuven, Belgium, was to describe, analyse and improve the actual routine practice of chemotherapy administration. The article focuses on analysis and improvement of role performance of nurses. The process of chemotherapy was systematically assessed by means of a retrospective analysis of patient records. This was done for 61 patient records receiving 453 chemotherapy administrations. Five aspects of the role of oncology nurses were described and analysed: data collection for prescription of chemotherapy, communication of instructions, preparation of the cytotoxic treatment, administration of cytotoxics and post-chemotherapy assessment. Data analysis showed variability in relation to several role aspects. Standardization of procedures and information was introduced to improve role performance in several areas.